Adenosine is a neuromodulator that regulates neurotransmission and cerebral blood flow but the nature of adenosine signaling in the brain is not well characterized. Most studies have described long-term effects of activation of adenosine receptors or changes in adenosine basal levels. Recently, rapid changes in adenosine have recently been discovered but the function of these transient changes is not known. The long-term goal of this lab is to develop new microelectrode methods to understand the rapid dynamics of neuromodulation in the brain. The objective of this project is to investigate the formation and function of transient adenosine signaling. This research is innovative because it challenges the paradigm that neuromodulation by adenosine is slow and advances technology by employing novel electrochemical sensors that overcome critical instrumentation barriers of slow temporal resolution and low sensitivity. The central hypothesis is that transient adenosine release occurs throughout the brain, is regulated by adenosine receptors, and functions to modulate neurotransmission and blood flow on a rapid time scale. This hypothesis will be tested with three Aims. In Aim 1, electrically-stimulated adenosine release will be characterized in multiple brain regions. Pharmacological experiments will be performed in brain slices to test the mechanism of adenosine formation and the cellular sources in each region. In Aim 2, spontaneous adenosine transients will be studied in anesthetized rats. These transients occur without drugs but are more frequent after administration of an A1 receptor antagonist. This study will provide a better understanding of how adenosine receptors regulate transient adenosine release. The goal of Aim 3 is to determine the function of transient adenosine release. The two hypotheses are that adenosine modulates neurotransmission and blood flow. The effect of exogenously applied adenosine on dopamine neurotransmission will be tested in brain slices. In addition, the effect of transient adenosine release on blood flow will be studied n vivo. This research will result in a better understanding of the formation and function of transien adenosine release. Adenosine based therapeutics have been proposed as possible treatments for neurological diseases such as pain, Parkinson disease, Huntington's disease, and drug abuse. New insight into the time course of neuromodulation could lead to better manipulation of transient adenosine changes to mitigate diseases caused by impaired neurotransmission.